Bias/erase oscillator

Abstract

A low distortion sinusoidal oscillator made up of a two transistor negative resistance element combined with an LC tank for generating bias and erase signals for battery powered magnetic media recording apparatus.

What is claimed is: 
     
       1. An oscillator for providing low distortion sinusoidal signals for bias and erase in a battery operated magnetic recording apparatus, said oscillator comprising: a. tank means for determining oscillation frequency, said tank means including an inductance comprising an erase winding, and a capacitive voltage divider comprising a combination of first and second capacitors connected in series with said inductance, said tank means having an output derived from between said first and second capacitors; and   b. a differential pair of first and second transistors with said output of said tank means connected to the base of said first transistor, and an input to said tank means connected to the collector of said second transistor from between said first and second capacitors, and said inductance.   
     
     
       2. An oscillator according to claim 1 wherein the emitter of said first transistor is connected to the emitter of said second transistor through a third capacitor for allowing said first and second transistors to have a maximum AC gain regardless of DC bias. 
     
     
       3. An oscillator according to claim 1 wherein said tank means includes an inductance means connected to the collector of said second transistor for DC biasing the collector of said second transistor to a supply voltage. 
     
     
       4. An oscillator according to claim 3 including a first resistance connected to the base of said second transistor for biasing said second transistor to a reference voltage, and a second resistance connected to the bases of said first and second transistors for biasing said first transistor. 
     
     
       5. An oscillator according to claim 4 including variable resistance means for adjusting current through said first and second transistors, with one end of said variable resistance means being connected to ground and the other end being connected to the emitters of said first and second transistors through third and fourth resistances for splitting current through said variable resistance means approximately equally through said first and second transistors.